1,721,007 research outputs found
Specific contribution of the Lateral Entorhinal Cortex to episodic-like memory recall
Full text linkLa memoria episodica, quella straordinaria capacità di ricordare eventi ed esperienze specifiche avvenute in un particolare contesto, dipende dalla corteccia entorinale (EC), una struttura che funge da collegamento funzionale tra l’ippocampo e regioni sensoriali nel cervello. Tradizionalmente, si è sempre ritenuto che la corteccia entorinale laterale (LEC) e la sua controparte, la corteccia entorinale mediale (MEC), svolgessero ruoli ben distinti nel trasmettere informazioni all’ippocampo. Si pensava, infatti, che la MEC fosse specializzata nel processare informazioni spaziali, mentre la LEC nel gestire i dettagli contestuali. Tuttavia, studi recenti hanno messo in dubbio questa visione semplicistica, sostenendo che la LEC possa avere un ruolo più diretto nell'integrare informazioni diverse per formare un'esperienza coerente ancor prima che tali informazioni raggiungano l'ippocampo.In questo studio, abbiamo indagato il coinvolgimento della corteccia entorinale nel processo di memoria simil-episodiche utilizzando il topo come modello animale e il test di riconoscimento oggetto-posizione-contesto (OPCRT) come paradigma comportamentale consolidato per lo studio della memoria simil-episodica nei roditori. Per identificare un collegamento tra l'attivazione della corteccia entorinale e il processo di memoria, abbiamo utilizzato la proteina c-fos come marcatore dell'attività neuronale e ne abbiamo osservato i cambiamenti nei livelli di espressione nell'EC dopo l'esecuzione dell'OPCRT. Abbiamo osservato che i topi sottoposti al test OPCRT possedevano un numero maggiore di cellule c-fos-positive nel LEC rispetto ai topi di controllo rimasti all’interno delle loro gabbie. In particolare, abbiamo osservato che l'aumento della marcatura per c-fos era presente esclusivamente nella LEC e non in altre regioni corticali come la MEC o la corteccia visiva primaria (V1), supportando fortemente l'idea del coinvolgimento specifico del LEC nel processo di memoria simil-episodica.Inoltre, abbiamo individuato cambiamenti nella plasticità sinaptica nel circuito LEC. Utilizzando registrazioni di potenziale post-sinaptico eccitatorio di campo (fEPSP) in fettine cerebrali contenenti l'EC, abbiamo scoperto che i topi esposti all'OPCRT mostravano una significativa riduzione della potenziamento a lungo termine (LTP) negli strati superficiali della LEC 12 ore dopo l'acquisizione della memoria. Inoltre, la diminuzione della LTP era specifica per il gruppo OPCRT e assente negli animali di controllo, ed era associata a un aumento della trasmissione sinaptica basale. Questi cambiamenti erano reversibili e tornavano a livelli di controllo 48 ore dopo l'esecuzione del compito, quando i topi non potevano più richiamare il ricordo, suggerendo che un'elevata trasmissione sinaptica possa svolgere un ruolo cruciale nel richiamo della memoria episodica.Infine, abbiamo condotto manipolazioni chemogenetiche dei neuroni coinvolti nell’apprendimento di una specifica memoria nella LEC, ovvero i neuroni attivati durante la fase di apprendimento del paradigma. I risultati hanno dimostrato che l'inibizione di tali neuroni del LEC è in grado di compromettere le prestazioni dei topi nel test di richiamo della memoria, mentre la loro attivazione è in grado di facilitare il richiamo della memoria stessa, fornendo prove conclusive dell'esistenza di un engramma di memoria simil-episodica nella corteccia entorinale laterale.Insieme, queste scoperte offrono prove convincenti del ruolo centrale della LEC nel processo di apprendimento di memorie simil-episodiche e nella loro integrazione nella più ampia rete di memorie episodiche.Episodic memory, the extraordinary capacity to recall specific events and experiences in a particular context, relies on the entorhinal cortex (EC) as a crucial bridge connecting the hippocampus and other sensory processing regions in the brain.Traditionally, it was believed that the lateral entorhinal cortex (LEC) and its counterpart, the medial entorhinal cortex (MEC), performed distinct roles in relaying information to the hippocampus. The MEC was specialized in processing spatial information, while the LEC was thought to handle contextual details. However, recent evidence challenges this simplistic division, proposing that the LEC may have a more direct role in integrating diverse information to form a coherent experience even before reaching the hippocampus.In this study, we investigated the entorhinal cortex’s involvement in episodic-like memory processing in mice, utilizing the object-place-context-recognition task (OPCRT), a well-established behavioral paradigm for studying episodic-like memory in rodents. To identify a link between entorhinal cortex activation and memory processing, we employed the protein encoded by the immediate early gene (IEG) c-fos as a marker of neuronal activity and observed its level in the EC after executing the OPCRT. Our results showed that mice engaged in the OPCRT task exhibited a higher number of c-fos-positive cells in the LEC compared to control mice confined to their home cages. Remarkably, the increase in c-fos staining was specific to the LEC and not observed in other cortical regions like the MEC or V1, strongly supporting the notion of the LEC’s specific involvement in episodic-like memory processing.Furthermore, we observed changes in synaptic plasticity specific to the LEC circuitry. Using field excitatory post-synaptic potential (fEPSP) recordings in brain slices containing the EC, we found that mice exposed to OPCRT displayed a significant reduction in long-term potentiation (LTP) in the superficial layers of the LEC 12 hours after memory acquisition. Notably, the decrease in LTP was limited to the OPCRT group and absent in control animals, and was associated with an increase in basal synaptic transmission. Interestingly, these changes were reversible and returned to baseline 48 hours after task execution when mice could no longer recall the memory, suggesting that heightened synaptic transmission may play a crucial role in episodic memory recall.Finally, we conducted chemogenetic manipulations of LEC learning-tagged neurons, i.e. those activated during the learning phase of the paradigm. The results demonstrated that the inhibition of LEC neurons impaired the mice’s performance in the memory task, while their activation facilitated memory recall, providing conclusive evidence of the existence of an episodic-like memory engram in the lateral entorhinal cortex.Together, these findings offer compelling evidence of the central role of the LEC in episodic-like memory processing and its integration into the broader episodic memory network
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Emerging Roles of Extracellular Vesicles in Alzheimer’s Disease: Focus on Synaptic Dysfunction and Vesicle–Neuron Interaction
Full text linkAlzheimer’s disease (AD) is considered by many to be a synaptic failure. Synaptic function is in fact deeply affected in the very early disease phases and recognized as the main cause of AD-related cognitive impairment. While the reciprocal involvement of amyloid beta (Aβ) and tau peptides in these processes is under intense investigation, the crucial role of extracellular vesicles (EVs) released by different brain cells as vehicles for these molecules and as mediators of early synaptic alterations is gaining more and more ground in the field. In this review, we will summarize the current literature on the contribution of EVs derived from distinct brain cells to neuronal alterations and build a working model for EV-mediated propagation of synaptic dysfunction in early AD. A deeper understanding of EV–neuron interaction will provide useful targets for the development of novel therapeutic approaches aimed at hampering AD progression
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Conservative management of pneumoperitonitis after percutaneous transhepatic insertion of metallic biliary stents
No full textThe occurrence of pneumoperitoneum after a percutaneous transhepatic intervention is an exceptionally rare event. Generally it resolves spontaneously or with minimally invasive management even in symptomatic conditions (pneumoperitonitis); resorting to surgical approach is exceptional. What is still unclear is the question as to whether the airflow has an intestinal or atmospheric source. Our report lends support to the former hypothesis, as argued hereafter
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